The Optical Magic Lantern Journal (January 1892)

2 The Optica. Magic Lantern Journal and Photographio Enlarget.. from his lips ; no one was injured. of the case, as told by Mr. Bridge, will be found on another page. 2 * & In the course of a letter from Hon. Slingsby Bethel, commenting upon the recent explosion, he suggests that gas-bags should never be placed ' in the midst of an audience, as they can easily be placed out of harm’s way in a side room, or even outside in a yard, and that the lantern should always be behind the audience. Speaking of jets, Mr. Bethel says that the blow-through is sufficiently powertul for the majority of country entertainments. Some twenty-five years ago he had constructed a blow-through jet, which was in no way inferior to the ordinary mixed jet. In it the oxygen nipple terminated one-eighth inch from the hydrogen orifice. s cd s ANOTHER startling invention in the lantern line is promised by a London firm of manufacturers. A hundred slides are placed in a box at the lantern. These are automatically brought into position in the lantern, and then passed into another box, all by the mere pressure of an electric button by the lecturer. This arrangement will enable a lecturer to operate his lantern, no matter how far he may be from it, and ensure the slides being revealed upon the screen exactly at the time required. All this we are promised for next season; meantime, a gentleman whose name is well known in the lantern line, has almost completed a model, and we have been promised an invitation to witness its performance as soon as it is finished. We presume, however, that it will be requisite to keep a boy stationed at the lantern to turn the lime and attend to any focussing which may be required, unless these, too, are done by electric current. * 2 OxyYGEN, it has long been known, stands alone’ among the gases in being slightly magnetic. An experiment has, however, been made by Professor Dewar, of Cambridge, which very strikingly illustrates this property. Mr. Dewar has succeeded in reducing this gas to a liquid condition. Under a temperature of 180 deg. Centigrade below zero, he poured the liquid oxygen into a shallow saucer of rock crystal, a mineral which it does not moisten or to which it does not adhere, and consequently maintains in connection with that substance a perfect spheroidal condition. It was naturally expected, considering the magnetic inclinations of the gas, that under magnetic stress there would be a total or partial arrest of the violent agitation caused by the ebullition of the mass of liquid oxygen, Something much more marked, however, happened; for on being brought The facts ' into relation with a powerful electro-magnet, the entire spheroid was literally lifted through the air, and remained adherent to the poles until dissipated by the heat of the metal. As all physicists know, iron and other metals lose their magnetism when red-hot. But this increase of power in a feebly magnetic gas when concentrated by cold is not paralleled by the behaviour of any other magnetic metal in solution. 10: Instructions for Inexperienced Lanternists. No. I. One of the first things for a tyro to learn in connection with lanterns is that outward show in a lantern is nocriterion as to its being a serviceable instrument from a lasting point of view, or its utility as an apparatus for optical projection. It is quite possible for an article of very inferior kind to be polished up to resemble (to an inexperienced eye), a highclass instrument, and many such are constantly being sold. It will be at once evident that these remarks in no way apply to recognised dealers and makers of lanterns, who having a reputation to sustain would not dream of selling anything which was not as represented. It is well-known that second-hand lanterns? can be obtained from dealers in second-hand general merchandise, and many of them are sad affairs, for the dealer, perhaps, knowing nothing about the requirements of a lantern, sells it merely on its own merits. In many cases the purchaser, who may, perhaps, have never before handled a lantern, but, being struck by the price asked, finds upon buying, that he has been sold, and that to put his apparatus in anything like working order, costs hin more than he could have purchased a new lantern for, had he in the first instance consulted some one who was conversant with the subject. We lately had a call from a youth who had been purchasing various parts of the outfit. The body he purchased at Holloway fair, the lens at an auction, the condenser from another source, and the lamp, &c., from other places. He informed us that he had a complete lantern, but as he could not get it to work, asked us to tell him what was wrong. The apparatus having been produced, we saw a tall antiquated tin lantern, with one of the condensers gone, a lamp which was propped up several inches witha piece of wood ; a very good-looking c.d.v. lens mount, in the outer end of which was stuck a small magnifying glass, the space between which and the lens mount was occupied by a ring of cork.